Cyclohexenes disubstituted in the 4-position by cyano or carbamyl groups



Patented June 6, 1950 POSITION BY GROUPS CYANO OR CARBAMYL Alan E.Ardis, Akron, Ohio, assignor to The B. F.

Goodrich Company, New York, N. Y., a corporation of New York No DrawingApplication February '7, 1948, Serial No. 6,999

4 Claims'. (Cl. 260464) This invention relates to a method for thepreparation of vinylidene cyanide which method involves the pyrolysis ofcertain 4,4-disubstituted cyclohexenes. r

I' have discovered that vinylidene cyanide (also known as. Ll-dicyanoethylene a liquid compound of the formula when present in monomericform, may be readily prepared in excellent yields by the pyrolysis ofdisubstituted cyclohexenes of the formula wherein each oi'I'X and Y isselected from the class consisting of --CN and radicals, X and Y beingthe same or different.

The lfi-disubstituted cyclohexenes which are pyrolyzed to obtainvinylidene cyanide in accordance with this invention have not heretoforebeen prepared but may be obtained in a variety of ways. One method ofarriving at compounds in which X and Y are the sameconsists in reacting4;,4.-dicarboxy cyclohexene, a known compound, with thionyl. chloride orother substance which will replace the hydroxyl hydrogen atoms withchlorine, and then reacting the 4,4-cyclohexene dicarbonyl chloride'thusformed with ammonia. The new compound wherein X and Y are both i. e.,4,4-d-icarbamyl. cyclohexene, is thereby obtained. From this diamide thedinitrile, 4,4- dicyano cyclohexene, the new compound wherein both of Xand Y are --CN, is obtained simply by dehydration in'the usual manner.

The new compound wherein X and Y are dif-'- ferent, that is,4-oyano-4-oarbamyl cyclohexene,

may be prepared, for example, by reacting butadiene-1,3 with anaykyl-ester of alpha cyano acrylic acid tthe preparation of which isdisclosed in my copending applications, Serial No. 731,863,-

cyclohexene isalso obtainable by dehydrating the 4.-cyano-4-carbamylcyclohexener The reactions described above may be formulated as follows:

00 on 0-0 01- 000E soon mm I O 0 NET Dehydrating agent OHFCH-OEEOHzcapo-( s i ON ON OOOR a ooNn:

As disclosed hereinabove, vinylidene cyanide is obtained by thepyrolysis of any of the compounds of the general formula wherein X and Yhave the meaning set forth hereinabove. Monomeric vinyli'den'e cyanideis easiest obtained in highest yield when the com-' pound pyrolyzed is4,4-dicyano cyclohexene, although vinylidene cyanide may also be readilyobtained in good yield by the pyrolysis of the other compounds of thisformula.

Thenproducts of the pyrolysis reaction are vinylidene cyanide andbutadiene-lfi. In addition to vinylidene cyanide and butadiene, water isalso obtained when the starting compound is a disubstituted cyclohexenecontaining one or more carbamyl (--CONH2) groups. The pyrolysis reactioncan be conducted in several different manners. For example, one

method involves passing vapors of the 4,4-disub- V glass pyrolysis tubeinstead of a metal tube, or pyrolyzing the starting material over a hotresistance wire. The pyrolysis reaction is preferably conducted atreduced pressures, and espe cially from 2 to 50 although pressures up toand including atmospheric pressure are operative.

The temperature at which the pyrolysis is conducted may be variedwidely. Temperatures in the range of 400 C. to 800 C. are operative withthe preferred range being from 550 C. to 700 C.

The product of the pyrolysis, usually collected as a liquid, is amixture of vinylidene cyanide, unreacted 4,4-disubstituted cyclohexeneand butadiene, water also being present when the starting materialcontains one or more --CONH2 groups. The vinylidene cyanide can beseparated from the pyrolysis product by several methods. For example, apreferred method consists in evaporating oil the volatile butadiene andfractionally distilling the remainder of the pyrolysis reaction mixture,preferably at reduced pressures, whereupon a fraction consistingsubstantially of vinylidene cyanide is obtained.

A second useful method consists in extracting the vinylidene cyanidefrom the reaction mixture by the use of a solvent, preferably one fromwhich the vinylidene cyanide will crystallize. This is done, forexample, by mixing the liquid product and a substance such as drytoluene or similar aromatic hydrocarbon, preferably in equal volumes,and cooling the mixture to a temperature of ap roximately 40 C.whereupon monomeric vinylidene cyanide separates from the liquid mixturein the form of crystals which are easily isolated, for example, byfiltration. High yields of very pure vinylidene cyanide, in themonomeric form, are obtained by this method.

vinylidene cyanide polymerizes quite rapidly in the presence of water toform a solid polymer. Consequently when water is present in thepyrolysis reaction mixture, vinylidene cyanide may be isolated byallowing polymerization to proceed and then separating the solidpolymerized vinylidene cyanide from the other products by filtering orthe like. The polymer may then be depolymerized by heating, preferablyat 170 to 250 0., to obtain monomeric vinylidene cyanide.

When using other methods of separation, it is desirable that thevinylidene cyanide be stabilized against polymerization from the timethat it is formed. This may be accomplished by using a suitablevinylidene cyanide stabilizer (that is, a polymerization inhibitor)which may be mixed with the 4,4-disubstituted cyclohexene prior topyrolysis or placed in the receiver for the pyrolysis reaction product.Such a stabilizer is also preferably present in the receiver used tocollect the vinylidene cyanide when it is separated by distillation.Suitable vinylidene cyanide stabilizers include phosphorus pentoxide andphosphorus pentasulfide, which are referred, as well as antimonypentoxidaconcentrated sulfuric acid and other materials reactive withwater, since polymerization is catalyzed by even small amounts ofhydroxyl ion. The stabilizer may be present in any desired amount but ingeneral as little as 0.5 to 3.0% based on the amount of monomer issufiicient to prevent polymerization for extended periods of time.

The following examples are intended to illustrate the preparation of4,4-disubstituted cyclohexenes and the pyrolysis of such compounds tovinylidene cyanide. It is not intended, however, to limit the inventionthereto, for there are, of

course, numerous modifications. All parts are by weight.

Ewample I 116 parts of 4,4-dicarboxy cyclohexene, are refiuxed for 63hours With1650 parts of thionyl chloride. The unreacted thionyl chlorideis removed by distilling at reduced pressure. The residue is thendiluted with three times its volume of anhydrous ether and this solutionadded dropwise with stirring and cooling to a dry ether solution ofammonia. Additional ammonia is bubbled through the reaction mixtureduring the addition of the ethereal solution in order that an excess ofammonia can be maintained throughout the reaction. The solid which formsis filtered, washed with water and recrystallized from methanol. It isidentified as 4,4-dicarbamyl cyclohexene (nitrogen analysis: theory16.7%, found 16.8%) and is secured in substantially quantitative yield.

' Example II 120 parts of 4,4-dicarbamyl cyclohexene, obtained as inExample I, are mixed with 189 parts of phosphorus pentoxide as adehydrating agent, and the mixture fractionally distilled whereuponthere is obtained 60 parts of a fraction (B. P. 66 C./1 mm.) which uponpurification is identified as 4,4-dicyano cyclohexene (M. P. 36 C.;nitrogen analysis: theory 21.2%, found 20.1%).

Example III 4,4-dicyano cyclohexene, obtained as in Example II, ispyrolyzed by passing vapors thereof at 5 mm. pressure, over anickel-chromium wire maintained at a temperature of 650 C., thepyrolysis reaction product being collected in a receiver which is cooledin an acetone Dry-Ice bath.

The reaction product is allowed to warm up to room temperature and thendistilled at a pressure of 5 mm. into a receiver containing a smallamount of phosphorus pentoxide whereupon monomeric vinylidene cyanide(M. P. 8 C.; a

1 1.440) is obtained in good yield.

Example IV When 4,4-dicarbamyl cyclohexene as prepared in Example I ispyrolyzed as in Example II over a nickel-chromium wire at a temperatureof 600 C. in the presence of phosphorus pentoxide, vinylidene cyanide isagain obtained in substantial yield.

Example V heated in a steam bath for two hours, after which the bombiscooled, opened and the product distilled. 16 parts of4-cyano-4-carbethoxy cyclohexene (B. P. 91/1 mm., n=1.465) are obtained.

One mole of the 4-cyano-4-carbethoxy cyclohexene thus prepared is thentreated with 1.2 moles of concentrated ammonium hydroxide. The solidthus formed is filtered, washed with a small amount of cold ethanol andthen recrystallized from methanol. It is identified as 4-carbamyl-4-cyano cyclohexene (nitr gen analysis; theory 18.7%, found 18.8%).

Example VI 15 parts of 4-carbamyl-4-cyano cyclohexene,

prepared as in ExampleV are mixed with 20 cresyl phosphate to give anintimate mixture... This mixture is then distilled giving a 64% yield of4,4-dicyano cyclohexene (B. P. 66/1 mm., 110/11 mm.).

Example VI I Example VIII The pyrolysis of Example VII is repeated inthe presence of 1 part of phosphorus pentoxide. Upon distillation of thereaction product at a pressure of mm. a 58% yield of monomericvinylidene cyanide (M. P. 8 C. n=1.4440) is obtained. 7

When 4-cyano-4-carbamyl-cyclohexene prepared as in Example V ispyrolyzed under the conditions set forth hereinabove and the reactionproduct distilled, vinylidene cyanide is also obtained as the principalproduct.

vinylidene cyanide prepared by the method of this invention is veryvaluable for the preparation of polymers and copolymers suitable assynthetic rubbers, synthetic resins, and plastics. Furthermore,polymeric vinylidene cyanide and copolymers of vinylidene cyanide andother materials polymerizable therewith, may be spun into syntheticfilaments which possess many valuable properties including great tensilestrength, flexibility, and resistance to chemicals. Monomeric vinylidenecyanide, as well as the compounds from which it is obtained as disclosedherein, 40

may also be used for insecticidal and fungicidal purposes as well as formany other uses.

Although specific examples are included herein, it is not intended tolimit the invention thereto, for numerous modifications will be apparentto those skilled in the art, and are within the scope of the appendedclaims.

6 I claim: 1. A compound of the formula wherein Xand Y are selected fromthe class consisting of -CN and --CON-H2 groups.

2. 4,4-dicyano cyclohexene of the formula 3. 4-cyano-4-carbamylcyclohexene of the formula C ONH:

4. 4,4-dicarbamyl cyclohexene of the formula C O NH: @O O NH:

ALAN E. ARDIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,217,632 Wolfe Oct. 8, 1940.2,264,354 Alder et a1 Dec. 2, 1941 2,385,552 Spence et a1 Sept. 25, 19452,410,820 Harris Nov. 12, 1946 2,447,196 Martin et al. Aug. 17, 1948OTHER REFERENCES Ostling, Chem. Abstracts, vol. 15, page 2829 (1921).

Bachman et al., Chem. Abstracts, vol. 34. Cols.

Gallagher, Chem. Abstracts, vol. 37, 0'01. 199'? (1943).

1. A COMPOUND OF THE FORMULA